Concepts, processing and results

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Abstract
Investigations have been carried out in the Wadi Araba–Jordan Graben area to trace the relationship between diagnostic signals received from Landsat Thematic Mapper (TM) data and several mineralized ground districts. To meet the objectives, different approaches, involving ratioing, principal component analysis and IHS-decorrelation processing, are used to enhance diagnostic features associated with hydrothermally altered areas. Using ratio techniques the best suited approach is given by a colour combination of band ratios 5/7, 4/3 and 7/4. In principle, comparable results can be generated by a combination of the principle components (PCs) 2, 4 and 3 in this succession. However, the ratio and PC approaches often fail to accentuate clearly the diagnostic features. Main reasons are attributable to similarities in relative intensities of vegetation and minerals and to disadvantages that arise through the techniques themselves. Decorrelated and filtered colour composites of TM bands 1, 4 and 7 have proved to be more successful for delineation of known and unknown mineralizations by the presence of alteration guide minerals such as iron oxides and phyllosilicates. In addition, the resulting final products of the decorrelation concept can be used for carefully directed field work, as spectral and structural information are enhanced simultaneously.

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